This might sound like a stupid question how do you tell the difference between a mild steel di filippo exhaust and a stainless steel one there all painted black need to know as i'm looking at buying one thanks

thanks for the info checked with supplyers in the eastern states and comfirmed that the magnet test won't work , magnet will still stick to there stainless steel exhaust even being 304 grade we still carry magnectic particles but cat is only made in stainless and the mufflers barrells will be polished and mild steel ones are all black .

304 can become magnetic from cold working including bending and shot blasting (formation of martensite), it is NEVER magnetic in it's natural form. So in theory the straight pieces would be less magnetic (if at all) than the bent sections. Even if blasted before paint the straight sections shouldn't be very responsive to a magnet. Stainless in most commercial grades is a poor choice for an exhaust anyway as exhaust fumes contain sulphur, sulphur eats nickel.

Also with the magnet test it helps to try it on mild steel first to see how much 'pull' it actually has, then compare to what your testing. Which is all useless unless it's sitting in front of you.

My 316 exhaust is fairly rusty. My 304 cat is worse. Titanium or Inconel is the best material for the job. Alot of high end ricers run titanium exhausts.

Back on topic.... glad you got it sorted.

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Not to get technical, but according to chemistry alcohol is a solution.

304 can become magnetic from cold working including bending and shot blasting (formation of martensite), it is NEVER magnetic in it's natural form. So in theory the straight pieces would be less magnetic (if at all) than the bent sections. Even if blasted before paint the straight sections shouldn't be very responsive to a magnet. Stainless in most commercial grades is a poor choice for an exhaust anyway as exhaust fumes contain sulphur, sulphur eats nickel.

Also with the magnet test it helps to try it on mild steel first to see how much 'pull' it actually has, then compare to what your testing. Which is all useless unless it's sitting in front of you.

My 316 exhaust is fairly rusty. My 304 cat is worse. Titanium or Inconel is the best material for the job. Alot of high end ricers run titanium exhausts.

Most exhaust places use 400 Series stainless steels for exhausts....it is magnetic.The original headers on the Holden VK Commo's with the 6 cylinder EFI engine were made from 400 series s/s....and they went rusty too.I used 316 grade s/s on my exhaust, and it hasn't gone rusty...... yet.

I've read that about the 400grade cjh but never met anyone locally that uses it, probably because it still rusts anyway. The VK manifold would have been far ahead of its time?

The other thing that ruins all grades of stainless is heat cycles, it's not the getting hot but the cooling down, particularly with duplex grades. It never gets a chance to return to it's original grain structure therefore in basic theory getting weaker every cycle (enlarged grain) & also vibrations cause work hardening which both lead to cracking.

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Not to get technical, but according to chemistry alcohol is a solution.

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